Process for defibering lignocellulose while subjected to steam and a digestive chemical



Patented Nov. 23, 1948 PROCESS FOR DEFIBERING LIGNOCELLU- LOSEWHILE SUBJECTED TO STEAM AND A DIGESTIVE CHEMICAL Henry E. Walter, Cloquet, Minn., assignor to Wood Conversion Company, Cloquet, Minn., a 1 corporation of Delaware No Drawing. Application August 3, 1940, f

Serial No. 351,239 l 9 Claims.

The present invention relates to the production of fiber from lignocellulose materials, and more particularly from wood, generally in a gaseous environment having moisture or water vapor,

and particularly in steam, and in the presence of a chemical active upon the substance of the lignocellulose.

Heretofore, it has been proposed to reduce wood,

straw, cane, bagasse, grasses and the like to fiber mechanically in the absence of suspending water. This has been effected by rotary means at elevated temperatures of 212 F. and over, in an environment of gas, particularly steam in a pressure chamber, employing the temperature to soften the ligneous content of the raw material to ease the mechanical process. Such procedure is offered as a substitute for wet grinding processes and for chemical cooking processes. Qne aim of the process has been to operate quickly upon the raw material, in a period of 40 seconds more or less, to minimize or avoid incidental chemical action upon the material or incidental change in the material. Such a process and a machine therefore are described in the U. S. Asplund Patents No. 2,008,892 and No. 2,145,851. Auxiliary to these is a third U. S. Asplund Patent No. 2,047,170, relating to carrying out the process in the presence of fusible sizing agents such as rosin,

wax, and the like to size the resulting fibers.

Such prior art procedure and its products have been studied, and it has been determined that the product is of a predetermined character because of chemical action induced by the heat from said conditions of operation, involving the natural constituents of the lignocellulose. In detail, these reactions and the effects thereof are complex, but in general it may be stated that they are effected in an acid medium and produce more acid, all resulting from the natural constituents of the lignocellulose material. Acid with and without heat in general has an embrittling effect upon lignocellulose and cellulose- Accordingly, the said steam defibering process produces a product which is the result in part at least, of an acid condition at high temperature. v

The general object of the present invention is to employ one or more chemical agents in such a defibering process, which is effective to alter the conditions whereby a different fiber product results.

An object of the present invention is to add one or more chemical reagents with the lignocellulose or prior to completion of its defibration, which chemical material alters the acid condition present in the substance of, and resulting from, the lignocellulose, and which imposes new controlling conditions. The reagents may act not only to generate more acidity, but to buffer the acidity, or to neutralize it in whole or in part, or to provide an alkaline condition.

30 fractionation for special-purpose fibers.

A further object of the invention is to add an agent in quantity and character according to the results desired, whereby a wide variety of fiber products of varying utilities, may be obtained.

A particular object of the invention is to employ a reagent which provides'in the presence of lignocellulose a supply of base to neutralize acidity of, or resulting from, the lignocellulose in the mechanical defibering process, or in the mechanical defibering process in the presence of the agent.

A further object of the invention is to employ alkaline reacting substances in amount from more to less than sufficient to bring the dis charged fibers to a neutral condition. 1

Still another object of the invention is to employ a chemical which modifies the lignocellulose. Still another object is to employ a chemical having a reducing power, or an oxidizing power.

reducing power.

The fiber from such a process as that of Asplund is useful in many directions. It may be dried directly as discharged, and used for thermal or sound insulation, or as a raw material for The moist fiber as discharged may be felted to mats directly, with or without adhesives or other added agents. The moist fiber as discharged may be taken up in water or chemical treating solutions for further modifying the properties, or for various uses. In water for example, the fiber may be refined or hydrated for forming board or paper by wet-felting processes.

The character of the mechanically produced fiber for these various uses greatly influences the processing of the fiber and the products thereof. For improvements in the processing and in the products, an alteration of the fiber during its production may be made by the present invention.

It is, therefore, a general object of the invention, by adding chemicals, chemically to alter lignocellulose material while reducing it to fiber in a gaseous environment including moisture or water vapor at from normal to elevated temperature of 212 F. or higher.

Various other and ancillary objects and advantages of the invention will become apparent from the following description and explanation of the invention.

In carrying out the invention, it is to be understood that the mechanical defibering action reduces the wood or other material quickly to fibrous condition and simultaneously mixes the material and fiber with any other material present. The amount of water present may only be that entering with green wood, or the equivaof any solid chemical added, and an inappreciable dilution of any chemical solution added. Thus, a small amount of chemical may be eiliciently used to act upon the lignocellulose. There is no part of the chemical not in contact with the lignocellulose as is the case where chips are suspended in cooking liquors. There is no time required for cooking liquor to penetrate the wood substance to exert its effect. There are no eifecti-ve over-action of some material, as at the surface of chips, and under-action as at the center of chips. All the substance of the wood is exposed to the action of the chemical by the mechanical defibering means. These function to exert tremendous pressures on the material, which if softened, as by steam, is quickly mixed with chemical. In the Asplund machine having disks, as the fiber leaves the disks, it is exposed to the high temperature, to the chemical distributed on it, and to the moist gaseous environment, whereby chemical efiects on the substance are favored. The time for which this may occur in any particular machine, may be controlled by the rate of operations in feeding and discharging.

The Asplund machine in particular permits chemicals as solids or solutions to be fed into the preheating magazine of the machine with the wood or other lignocellulose, which is highly compressed into a pressure-sealing plug. On entering the magazine the material is immediately exposed to the high temperature therein, and becomes heated as it is advanced by mechanical means toward the defi-bering disks. The time in the preheater until defibered, is of the order of less than one minute. In cases where strong chemicals, such as solid caustic soda fed in with wood chips, produces an undesirable reaction prior to defibering, this effect may be avoided. In any case, the chemical may be introduced as a separate ingredient, either as a solid or in solution, to the material at least prior to completion of defibration, and permissi bly after the beginning of defibration. In the Asplund machine having one rotary plate and one stationary plate, the latter may be used with openings for such introduction. Feeding means for chemical may be carried into the machine to discharge chemical onto the lignocellulose material in the defibering zone. However, as a matter of fact, it has not been found to be an absolute necessity to avoid feeding caustic soda as solid, or as a 50% solution, mixed with wood chips, into the Asplund machine.

DIGESTING CHEMICALS Practically all favorable cooking processes for wood are alkaline, or neutral with a high content of salt of weak acid and strong base, or are several modifications. Neutral type processes are represented by the sodium monosulilte base processes, which are more favorable when slightly alkaline with sodium carbonates. Acid processes are represented by the acid-suliite salts of sodium. calcium or magnesium, and more rarely ammonium.

All of the above types provide available base for neutralizing the natural acid character of wood and other lignocellulose. This is even true in the case of the normal and acid sulfite salts. In such cases, the sulfite radical becomes available for combination with lignin of the lignocellulose, leaving the basic elements of the salts as available alkali equivalent for neutralizing acidity of the substance, as present or developed. The salts such as carbonates of magnesium, alkali, metals and alkaline-earth meals, likewise provide available alkali equivalent for neutralizing acidity in the lignocellulose material.

One advantage of the present invention is the facility for quickly securing fiber having been treated with small, rather than large, amounts of chemical. In a water suspension of lignocellulose to secure a result from small amounts of chemical, it is necessary to suspend formed fiber, or chips or the like not yet deflbered. The relative proportion of water to lignocellulose is so much higher than in the present invention, that the small amount of chemical is in very dilute solution. In the case of chips, the chemical will be expended first and largely on the outer portions of the chips, producing non-uniform results. That is one reason why, heretofore, strong chemical solutions have been required, accompanied by action in pressure digesters. In the case of fibers in suspension in dilute solution, the fibers must have been produced, and soluble material in the lignocellulose will enter the solution. Obviously, it is an advantage of the present invention that the fibers are produced in the presence of the chemical and small amounts of water, with preservation in the fiber of substantially all the solid contentof the original cellulosic raw material. The invention therefore provides a process for securing substantially maximum benefits from both small and large amounts of chemical agents without extracting material from the lignocelluglse, and with very uniform results from fiber to her.

The retention oi water extractable material in the fiber is an economic advantage avoiding waste in raw material, where the fiber is usedwithout an extracting aqueous treatment. It is an economic advantage in eliminating equipment, and operations. Also, the retention of water-extractable material in the fiber, including solubles resulting particularly from the chemical treatment, gives a firsttype of new fiber with extractable solubles, which solubles may be removed as a useful byproduct, leaving a second type of new fiber. These two types of new fiber may be used as raw material for structures, or for additional chemical processing, or for felting from water suspension, without, or with varying degrees of refinement or hydration.

MIXTURES OF CHEMICALS The present invention is not limited to use of one chemical at a time. Several may be mixed. Thus, sodium monosulfite may be mixed with so dium carbonate, or sodium bicarbonate, or both, or with sodium hydroxide, or with sodium hydroxide and a'sodium carbonate. Caustic sOda and calcium oxide or hydroxide may be mixed. Borax may be mixed with boric acid, or sodium monosulfite. Various other combinations may be used. Some combinations may be used wherein the several chemicals may interact, yet produce effective products. Thus, sodium bisulfite may be mixed with a sodium carbonate, every 2 moles of sodium bisulfite lost, producing one mole of sodium monosulfite.

INERT ADDITION AGENTS The use of chemical agents active on the lign'ocellulose does not bar the use of non-active agents. The chemical agents have been used simultaneously with added substance such as:

suspensions of rubber, rubber latex. asphalt, wax, protein, sodium pentachlorphenol, fireproofing agents, sodium silicofiuoride, rosin, and many others. These substantially inert agents may be employed to add certain preservative or resistant properties to the fiber, or to size them. Such additions are more particularly useful in the cases where the discharged fiber is used directly without a water extraction. However; where such addition agents are not water soluble, the fiber may be subjected to a. water treatment. For example, asphalt-treated fibers may be hydrated and formed into board as disclosed in Heritage Serial No. 334,761, filed May 13, 1940, now Patent No. 2,402,160. The use of rubber dispersions and latex is described in Heritage Serial No. 336,577, filed May 22, 1940, now Patent No. 2,375,414. The use of proofing agents for mold and decay, such as pentachlorphenol, is described in Heritage Serial No. 345,610, filed July 15, 1940, now abandoned. The use of fireproofing agents is described in Heritage-Walter Serial No. 332,682, filed May 1, 1940, now abandoned, and Serial No. 332,683, filed May 1, 1940, now abandoned.

In some circumstances the inert agent and the chemical agent may be combined for some convenience or advantage, the combination being subject to effective action as a chemical, by the presence of the material being deflbrated. For example, protein may be dispersedin alkali, or rosin may be used as a soap. The fiber or lignocellulose, being or developing acid, acts like added alum in the case of paper pulp sizing, to effect a so-called precipitation of the size. Thus, the

alkali present with protein, however it is assoelated, or the alkali in a rosin or other soap. Drovides base for neutralizing acid in the llgnocellu- INDICATIONS OF FIBER CHANGE A mass of fiber has mass properties which depend upon the individual fibers, the sizes of the individual fibers, and the state of aggregation of the fibers. Consequently, a determination of a mass property means little without knowledge of many other properties and of inter-relationships of properties. Individual fibers vary in size and character, in part according to the original location in the wood. Therefore, measurements of properties of individual fibers, may vary from fiber to fiber. Practically, all measurements are made on masses of fiber for mass properties, or on many fibers, to strike an average. For example, the acidity of a mass must be the average measurement resulting from the acidity of the fibers exposed to influence the test. It has been found that in spite of all these handicaps. the trends of changes by treatment or other cause, are evidenced by consideration of not only a single property, but also numerous properties as a group. The following discussions and definitions 6 are intended to be an aid in understanding the meaning of the properties reported hereinafter.

The term pH of the fiber is in effect the pH of a water extract of the fiber determined as follows:

A sample of 10 grams of oven-dry fiber, or 10.7 grams of air-dry fiber, is extracted for hours at 50 to 60 C. in cc. of distilled water which has been boiled. The water is separated, stoppered and cooled to room temperature, and its pH is measured.

The measurement ofinsulating value, also known as It-value" is made on a fiber mat of l-inch thickness at a density of 3.8 lbs. per cu. it. (which is 3.15 board-feet per pound. It is defined in terms of heat transmitted in B. t. u. per sq. ft., per l-inch of thickness, per 1 F. temperature differential, per hour, when the test sample is columns as a result of the compression are cor related to the density of the columns. From the data the properties are calculated.

"Sliding friction" indicates the surface charac- .ter of a mass of fibers to exhibit friction, as it does on the cylinder in compressing.

Free-footage" is an extrapolated density value, expressed as a reciprocal density in board-feet per pound of fiber" when the fiber is unfelted by pressure other than its own weight. It is akin to fiufilness."

Specific elasticity (Kit) is an indication of the elastic properties when the fiber being compressed is at an arbitrary reciprocal density of 3.15 board feet per pound.

Absolute elasticity is an index, or an indicative slope of a line produced in the mathematical solution, on which line the value Kn is read.

Specific felting (Kr) is an indication of the force which felts the fiber as it is being compressed and at 3.15 board feet per pound.

Absolute felting" (Mr) is an index, or an indicative slope of a line produced in the mathematical solution, on which line the. value Kr is read.

Friability is a measure of the ease of the fiber to break as set forth in Anway U. S. Serial No. 290,999, filed August 1-9, 1939, now U. S. Patent No. 2,324,126, issued July 13, 1943. It involves a standardized pounding of the fiber, giving the rate of dust formation with pounding.

Permanence to heat" is an indication of how heat changes thefriability of fiber. It is the ratio of friability of a. specimen not heated to the friability of a. specimen heated at a given temperature for a given time. This is set forth also in said Anway Patent No. 2,324,126.

"Impact resistance" is related to compressive properties. It is determined as described in Anway U. S. Serial No. 313,919, filed January 15, 1940, now U. S. Patent No. 2,375,182, issued May 8, 1945. Briefly explained, a vertically axial container, carrying a. column of fiber to be tested is dropped repeatedly to give an impact of 1 footpound on the column. The fiber thus acquires a constant density or volume. The final density expressed as its reciprocal in board feet per pound of fiber at 1 foot-pound impact is the impact resistance adopted for comparisons of fiber.

"Coarseness modulus" or C. M. is an arbitrary but standardized measure of particle size distribution. The method and apparatus is set forth in Heritage U. S. Serial No. 336,495, filed May 22, 1940, now U. S. Patent No. 2,325,055, issued July 27, 1943. Briefly, a specimen is divided by screening, into fractions according to screen size, and the percents as fractions are weighted in totaling, to give a significant figure, larger as the general coarseness of the fiber increases. Numerous systems different in detail are used to classify fiber, but diiferent systems give correlatable values for conversion from one to another.

EXAMPLES EXAMPLE 1.-Sonnnu CARBONATE Wood chips were defibered as shown below, the fiber dried directly in a hot oven, and tested.

Sample 8-218 Usage of NmCOa, percent..- l 5 Fiber acidity as pH 4. 32 4. 89 7. 61 9. 57 Friability 0. 0160 0. 0233 0. 0389 0. 0091 Permanence to heat 0. 439 0. 633 1 1.010 0.362

1 Excess over 1.60 due to experimental error.

A usage over about 4% soda ash is necessary to neutralize the acidity of the wood used. The over-neutral fiber at pH 7.61 has a high permanence to heat. due to the fact that no acid is or becomes available to embrittle the fiber.

EXAMPLE 2.-CAUSTIC Sons Fibers made in the same way with and without 1% usage of caustic soda gave results as follows:

Sample 8-190 Usage of NaOH, per cent 0 1 Coefficient of sliding friction.... 0. 52 0. 37 Free-footage 8. l2 Specific elasticity (K s) 235 A olute Elasticity (Ma) 0.892 Specific felting (Kr)..-.- 47. 1 Absolute felting (M r) 0. 333

EXAMPLE 3.Cansr1c Soon on Sonnm SULFI'IE Peeled aspen wood as a control, with 5% usage of NaOH in one case, and 5.75% usage of sodium sulfite plus 0.15% usage of NazCOa (as mixed carbonates) in the second case, have been compared as follows: The fiber is first extracted with water by boiling for two hours, then it is hydrated for the purpose of making board and paper. On the basis of 100 parts of dry fiber, and upon aspen wood containing 20.7 parts of lignin and 51 parts of alpha cellulose, the following results are noted:

Sample 8-226 Parts by weight Control NaOH NaaSOa-i- 65 460 467 Fiber produced "l 90. 2 76. 0 81. 5 Lignin in fiber .J 16.9 14. 4 l5. 1 ubles: 9. 8 24, 0 18. 5 Carbohydrates in solubles 6. 0 17. 7 12. 9 Lignin 1n solublcs 3. 8 6. 3 5. 6 Composition:

Per cent Alpha cellulose 50. 6 67. 0 G2. 5 Per cent Li nin 18.7 19.0 18.5 Per cent arbohydrates not cellulose 24. 7 l4. 0 19. 0

Fibers produced as above in the Asplund machine, but washed with cold water (60 F.) in place of being extracted as above stated, are then refined in a ball mill in a standardized procedure and at 7.5% consistency in water without added agent. Refining continues until a slowness of 19 seconds (Williams slowness and porosity tester) is attained, and the time recorded. Before and after ball-milling the particle size as coarseness modulus is determined. The results of forming the fiber and refining are shown as follows:-

MAKING OF BOARD I The above fibers after hydration, without other treatment, are formed into boards of the charac-- ter referred to as insulation board. This comprises merely felting a slurry ofthe fibers on a wire in a suitable manner to provide roughly a board of /2-inch thickness. The wet mat thus formed is pressed to %-inch thickness. It is then dried in several ways. One extreme is to dry the mat without restraint, whereby it may swell or spring back, or shrink in drying, if it will. Another way is to dry with restraint on the wet mat. This may be by means to maintain constant thickness, or means to maintain constant pressure. The latter is preferred for comparisons, and is used at lbs. per sq, ft., to obtain the "restraint values given below.

UNRESTRAINED DRYING Sample 8-226 Control NaOH NazSOi-i- 475 476 47] Dried specimen weight in grams.-. 30. 4 31. 3 29. 7 Dried specimen thickness, inches... 0. 600 0. 533 0. 544 Density lbs./eu. ft 15. 4 17. 8 16. 5 Per cent increase over pressed wet thickness on:

(a) Releasing pressure 72. 0 50. 0 54.4 (b) After drying 60.0 42. l 45. 1

RESIRAINID Darmo Sample 8-226 Control NaOH NMSOH' Density of dried board, lbs/cu. it- 17. 23 22. 79 16. 95 Per increase over pressed wet thickness on drying with 100 lbs/sq. ft. pressure 34. 7 9. 9 l7. 3 Board Thickness in inches 0. 492 0. 383 0. 417 Plgsical Property Values in Bend- 2: Load in lbs. at elastic limit....- 14. 7 21. 12.0 Load in lbs. at point of rupture. 20 31. 6 18.0 Modulus of elasticity 33, 200 77, 200 43, 000 Modulus of transverse strength. 182 429 207 Modulus of rupture 248 647 311 The foregoing shows that the chemical treatment in forming o1 fiber, considerably strengthens and rigidifles the boards made from the fibers.

MAKING OF PAPER.

Paper has also been made from the same fibers as described above for board. The fiber as discharged from the machine was screened moist, to remove coarser particles, by use or a 12-mesh screen. The fines were washed in cold water, and at 7.5% consistency. the fibers were ball-milled, formed into sheets on a wire-screen, and dried directly from formation, without pressing and without restraint.

The following data concerns the three types referred to:

Sample S-226 used in the art. The sheets were made without the usual wet-pressing.

' ExAurLn 4.Somuu Surrrra, Sonnnvr Csasomrn To wood chips to be defibered is added a solution containing sodium monosulfite and a small amount of mixed carbonates of sodium, in the amount per cu. ft. of about 18.4 lbs of Na2SO3, and 0.5 lb. of mixed carbonates calculated as NaeCOs. The usages are 1.15% NazSOa and .031% NazCOa equivalent. The water thus introduced is not suflicient to suspend the wood or the fiber, nor to destroy the steam environment.

The efiect of the chemical is to increase the qualities of resilience and compressibilities, to raise the pH, and to lighten the color." It also improved the uniformity of defibering, for example, lessening sticks. It makes the fiber feel softer to the hand.

Wax added.In addition 2% usage of parafiln wax has been added to the above usage of the said sulfite solution, to add water-resistant properties to the fiber.

EXAMPLE 5.-CALc1uM Hynaoxmn Calcium hydroxide has been used in amounts bringing the fiber to a pH above'and below neutral. -"The samples S-202-48 and 51, given below, were made in accordance with the usage of /3% (based on dry wood) of sodium pentachlorphenol proofing agent for mold and decay in a 20% aqueous solution, as set forth in Heritage Serial Untreated E No. 345,610, filed July 15,1940.

463 Treated Treated Sample 8-202 pH:

Before washing 5. 25 7. 10 6. 05 After washing..-.-.--.. 0.50 0.00 40 40 48 51 After ball-milling l 5.86 5.90 6. 35 Minutes to attain slowness secmlds 255 Usage of 0& 011): 2.73 2,38 2,38 coarseness l Acidity of fiber as pH 7.18 7.08 0. 9 Before ball-milling 135 108 125 Fmwoomge 9.6 101 98 titfii'tiitm 4- se. as as 0 soueeasici a 0.313 by bau'mimng- 55 s ecmc felting 1 p) 43. 9 41. 3 35 A solute felting (Mr)--- 0. 254 0. 233 0.232 Thtckmiss in 017 014 016 Dust content in per cent 6. 6 6. 4 6. 7 We1ghtlnlbs./M sq. 0 12.13 12. 58 11. 56 Thermal conductivity (k n 0. 227 Q 5 g-$: f Friability 0.0028 0.0010 0.0200 8118 moms) 3M2 M22 31 5o Permanence to heat 0.04 0.05 0. lb Apparent density, lbs.

ream-weight per point (0.001 inch) 2.00 2. 2.08 Tear 16 sheets), grams on EXAMPLE 6.--BORAX Elrnendorf tester 12 36 24 Mullen burst, lhs., sq. in...- Less than 2 3.0 Less than 2 Mullenfwwr Borax has been used with and without other chemicals as shown by the following series:

Sample 8-230 Chemical used None.. Borax. Borax B0rax. B rax.

sage m Chemicalused.. 3% (100,... sage-- .0. pH, predried fiber. 5.02. pH, dried fiber 7.19. Fria llty 0.0410. Fire I)lesistanee (grams loss per min. burning 2.10.

rate Color (total reflectance), per cent 27.1.

From the foregoing, it will be seen that both treatments improve fiber which is generally unsatisfactory to make a testable sheet of paper,

per-making pulp comparable to those commonly improvement in color while introducing borax. It

. 11 shows that the presence of sodium sulfite with borax, gixes the whitest color of the series, substantially improved over no chemical usage, and the burning rate is materially reduced.

EXAMPLE 7.CAUSTIC Sons/mp Pxornm $12!:

EXAMPLE 8.-Cm-:mc1lr. SALTS Chemical salts of various types have measurable effects upon the fiber as illustrated below.

. 301 17 4" U a and Chemical Control Aluminum Sag NazSiOs steam,

' Sample 8-224-6 8224-11 8424-13 Free-footage (FF) 6. 97 6. 62 6. 40 Sgeciflc elasticity (KB) 84 g 42 43 A solute elasticity (M1).-." 0. 502 0. 544 0, 511 S inc ielting (Kr) 30 20 19 A solute felting (Mr) 0. 386 0. 372 0. 394 k-valuo 0. 246 0. 259 0, 254 Friability 0. 1105 2. 200 0. 1930 Impact Besistance. 3. 9 3.2 4.4 coarseness modulus M.) 96, 142 8B Hygroscopicity, per cent at eqliiilibriumz umidity 937-55" F. 19. 8 l7. 9 18. 9 Humidity 55 55 F--- 10. 1 6.8 7.9

EXAMPLE 9.NEUTRALIZING Cnamcars A comparative series of several chemical agents was made at the same time against a control, showing the pH raised toward or past the neutral point. with other properties as follows:

I chemical properties, or composition, all as exemplifled above. Not only is the fiber changed to adapt it to specific physical uses, but also to adapt it to making a better board and papen' to make it differently susceptible to other chemical change.

Lignocellulose is not a stable substance. It is impossible at boiling temperatures with water, to extract the water-soluble" content, in over 300 hours treatment, because the extracting action changes the composition to form more extract. Changing the water to fresh water even hastens the change in composition. Steam treatment at elevated temperatures makes such a change, evidenced by increasing the water-soluble content determined by a standardized extraction. Added chemicals in water, or in the presence of steam also hasten such a change, especially those providing available alkali. Therefore, one measure of the effectiveness of a chemical is to measure the water-extractable contents, by standardized procedures, of fibers produced in the same way, one without the chemical and one with the chemical. This simple analysis of the fiber for extracts of substance from the original lignocellulose, is an evidence of the chemical action, which conditions the fiber as to physical and chemical properties. The present invention contemplates the use in deflbering of chemicals which increase the water-soluble extractives. This has been illustrated and explained in Example 3.

It is of course to be understood that the hydration in water, and the felting from water, are merely convenient test procedures, and do not limit the invention. Hydration may be efiected with moist fiber in the absence of suspending Sample 8-218 19 ll 12 l3 14 20 Chemical Added None NmCO; NmAlO; C8(OH)2 Na;SiO; NaHCO; Usage in per cent 4. 0 4 3. 7 2. 8 2. 3. 2 Acidity of Fiber as pH 3. 8 7. 7 6. 2 7. 5 5. l 7. 5 coarseness modulus 197 229;. 203 173 208 210 Free-Footage 9. 7 8. 9 10. 3 9. 8 10.2 9. 1 Specific elasthiity (KI) 155 196 230 235 140 105 Absolute elasticlll? (MI) 0. 33 0. 40 0. 33 0. 35 0. 30 0. 34 Specific felting p) 43 49 96 62 53 30 Absolute-felting (Mr) 0.25 0. 29 0.27 0. 27 0. 24 0. 24 Friablllty 0- 0077 0. 0130 s 0. 0027 0. 0063 0. 0025 0. 0050 Peto heat 0. 097 0. 420 0.218 0. 197 0. 040 0. 234 Dust content in per cent 4. 5 5. 7 5. 2 6. 2 4. 5 5. 5 Impact resistance 3. 9 4. 0 3. 8 4. 0 3. 7 3. 0

The foregoing table indicates that the properties of the fiber are not dependent only upon the neutralization, or the pH, but also and in part upon the type of chemical added. The efiects produced by sodium aluminate are highly specific. The

. permanence to heat is greatly increased by partial and over-neutralization.

Examma 10.Car.cmu Canaomrs AND Wax Wood chips are defibered with a usage of 10% paraflin wax and a usage of 5% calcium carbonate, forming a sized fiber.

DISCUSSION addition, it is a reducing chemical, and this is believed to be in part the reason that a lightercolored fiber is produced.

The chemicals exert changes on the fiber. indicated by changes in physical properties, or

water. and felting may be done from suspension in other liquids, or gases, to form boards and papers, or other felted structures.

The invention is of course not limited to use of chemicals as solid, or in solution. The use of a sulfite salt is known to produce sulfur dioxide in the deflbering Asplund machine, making .the sulfur dioxide a gaseous reagent. The reagent may be any other gaseous one introduced into the machine, or generated therein. Thus, sulfur dioxide may be introduced as a gas. Ammonia gas may be used. It may be introduced as a gas, or as a solution in water, whereby it may become a gas in'the machine.

The mechanical deflbering may be accomplished in various machines which operate also to distribute chemicals or solutions. Machines or processes, like that of Asplund, but not operating the Respats apparatus and process of Respess U.

S. No. 1,976,297 are all useful. In the latter. wood Reference is made to my copending applications Serial No. 351,240, filed August 3, 1940, wherein the used caustic alkali is specifically claimed, and Serial No. 351,238, filed August 3, 1940, wherein the use of sulfites is specifically claimed. In the latter case an example is given where a usage of of a sulfite salt has been employed.

I claim:

1. The method of treating lignocellulose which comprises heating lignocellulose in the absence of suspending liquid and in an atmosphere of steam at an elevated temperature above 212 F. at which the lignacellulose is rendered plastic, and simultaneously defibering the plastic lignocellulose and incorporating substantially uniformly throughout the lignocellulose chemical reagent reactive therewith, whereby to produce chemically treated fibers without substantial loss of constituents of the original lignocellulose.

2. The-method of producing fiber which comprises supplying undefibered lignocellulose to a mechanical defibering device, supplying to said device a chemical which is reactive with lignocellulose and a fiber-producing digestant therefor other than water. mechanically defibering said lignocellulose in the absence of suspending water and in the presence of moisture ina. gaseous environment by operation of said device while rubbing and pressing said lignocellulose, while distributing said chemical digestant substantially uniformly throughout the lignocellulose as the latter is being defibered and while reacting said chemical digestant with said lignocellulose thereby to effect modification of the lignocellulose by reaction with saidchemical, whereby to produce a fiber of chemically modified lignocellulose,

said fiber containing substantially all the solidprises supplying undefibered lignocellulose to a mechanical defibering device, supplying to said device a chemical which is reactive with lignocellulose and a fiber-producing digestant therefor other than water, mechanically defibering said lignocellulose in the absence of suspending water in an atmosphere of steam at an elevated temperature above212 F. and at which the lignocellulose softens to a plastic state, said defibering being effected by operation of said device while rubbing and pressing said plastic lignocellulose and while distributing said chemical digestant substantially uniformly throughout the lignocellulose as the latter is being defibered and while reacting said chemical digestant with said lignocellulose thereby to effect modification of the lignocellulose by reaction with said chemical,

whereby to produce a fiber of chemically modified lignocellulose, said fiber containing substantially all the solid content of the original lignocellulose.

4. The method of producing fiber which comprises supplying undefibered lignocellulose to a mechanical defibering device, supplying to said fibering said lignocellulose in the absence of suspending water and in the presence of moisture in a gaseous environment by operation of said device while rubbing and pressing said lignocellulose, while distributing said chemical digestant substantially uniformly throughout the lignocellulose as the latter is being defibered and while reacting said chemical digestant with said lignocellulose, thereby to eifect modification of the lignocellulose including neutralization of at least apart of the acidity available therein, whereby to produce a fiber of chemically modified lignocellulose, said fiber containing substantially all the solid content of the original lignocellulose.

5. The method of producing fiber which comprises supplying undefibered lignocellulose to a mechanical defibering device, supplying to said while rubbing and pressing said lignocellulose,

device a chemical material, which material is a fiber-producing digestant therefor and which material includes available base for neutralizing ,while distributing said chemicaldigestant substantially uniformly throughout the lignocellulose as the latter is being defibered and while reacting said chemical digestant with said lignocellulose, said material being supplied in quantity to provide'fibers having a pH of at least '7, thereby to effect modification of the lignocellulose and the,

material includes salt of a strong base and a weak acid, mechanically defibering said lignocellulose in the absence of suspending water and in the presence of moisture in a gaseous environment by operation of said device while rubbing and pressing said lignocellulose, while distributing said chemical digestant substantially uniformly throughout the lignocellulose as the latter is being defibered and while reacting said chemical digestand with said lignocellulose thereby to efiect modification of the lignocellulose including neutralization by said base of at least a part of the acidity available in the lignocellulose, whereby to produce a fiber of chemically modified lignocellulose, said fiber containing substantially all the solid content of the original lignocellulose.

7. The method of producing fiber which comprises supplying undefibered lignocellulose to a mechanical defibering device, supplying to said device chemical material, which material is a fiber-producing digestant therefor and which material includes available base for neutralizing acidity of said lignocellulose, mechanically defibering said lignocellulose in the absence of suspending water in an atmosphere of steam at an elevated temperature above 212 F., and at which the lignocellulose softens to a plastic state, said defibering being eifected by operation of said device while rubbing and pressing said plastic lignocellulose and while distributing said chemical digestant substantially uniformly throughout the lignocellulose as the latter is being defibered and while reacting said chemical digestant with said lignocellulose thereby to effect modification of the acidity of said lignocellulose, mechanically dethe solid content of the lignocellulose including neutralization oi at least a part of the acidity available therein, whereby to produce a fiber of chemically modified lignocellulose, said fiber containing substantially all the solid content of the original lignocellulose.

8. The method of producingfiber which comprises supplying undeflbered li ocellulose to a mechanical defibering device, supplying to said devi e chemical material, which material is a fiber producing digestant therefor and which mat rial includes available base for neutralizing aci ty of said lignocellulose, mechanically deflbering said lignocellulose in the absence of suspending water in an atmosphere of steam at an elevated temperature above 212 F, and at which the lignocellulose softens to a plastic state, said defibering being eflected by operation of said device while rubbing and pressing said plastic lignocellulose and while distributing said chemical digestant substantially uniformly throughout the lignocellulose as the latter is being defibered and while reacting saidchemical digestant with said lignocellulose, said material being supplied in quantity to provide fibers having a pH of at least 7, thereby to effect modification of the lignocellulose and the provision of non-acid fibers containing substantially all the solid content of the original lignocellulose.

9. The method of producing fiber which comprises supplying undeflbered lignocellulose to'a mechanical deflbering device, supplying to said device chemical material which material is a fiber-producing digestant therefor and which material includes salt of a strong base and a weak acid. mechanically deflbering said lignocellulose 3 in the absence of suspending water in an atmospheer of steam at an elevated temperature above 212 F. and at which the lignocellulose softens to a plastic state, said defibering being effected by operation of said device while rubbing and pressing said plastic lignocellulose and while distributing said chemical digestant substantially uniformly throughout the lignocellulose as the latter is being defibered and while reacting said chemical digestant with said lignocellulose, thereby to eil'ect modification of the lignocellulose including neutralization by said base of at least a part of the acidity available in the lignocellulose, whereby to produce a. fiber of chemically modified lignocellulose, said fiber containing substantially all original lignocellulose.

HENRY E. WALTER.

18 REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 6,646 Herron Sept. 14, 1875 106,710 Meloch Aug. 23, 1870 296,780 Pond Apr. 15, 1885 417,282 Reed Dec. 17, 1889 1,016,178 Sammet Mar. 30, 1912 1,153,883 Arledter Sept. 21, 1915 1,539,633 Schooger May 26, 1925 1,654,624 Wells Jan. 3, 1928 1,785,544 Ellis Dec. 16, 1930 1,794,174 Hatch Feb. 24, 1931 1,872,996 Mason Aug, 23, 1932 1,913,607 McMillan June 13, 1933 1,982,130 Wollenberg Nov. 27, 1934 2,008,892 Asplund July 23, 1935 2,047,170 Asplund July 14, 1936 2,072,686 Robinson Mar. 2, 1937 2,080,078 Mason May 11, 1937 2,145,851 Asplund Feb. 7, 1939 2,164,040 Oilermanns June 27, 1939 2,228,349 Feldman Jan. 14, 1941 2,234,188 Morgan Mar. 11, 1941 2,265,622 Basler Dec. 9, 1941 2,315,372 Kressman Mar. 30, 1943 FOREIGN PATENTS Number Country Date 12,149 Australia Apr. 10, 1933 103,709 Australia Apr. 28, 1938 35,854 Germany June 10, 1886 393,159 Great Britain June 1, 1933 OTHER REFERENCES Der Papler-Fabrikant, g. 36, 1938, Tiel I, pages 519-531.

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